#include <iostream>
#include <vector>

using namespace std;

class int2
{
	public:
	int x;
	int y;
};

int main()
{
	int h, a, e;
	cin >> h;

	vector<short> common;
	for (int i = 0; i < h; i++)
	{
		common.push_back(0);
	}

	vector<int2> Adam;
	
	cin >> a;
	for (int i = 0; i < a; i++)
	{
		int2 in;
		cin >> in.x >> in.y;
		in.x--;
		in.y--;
		Adam.push_back(in);
	}

	for (int i = 0; i < a; i++)
	{
		for (int k = Adam[i].x; k < Adam[i].y; k++)
		{
			common[k]++;
		}
	}

	vector<int2> Eva;

	cin >> e;
	for (int i = 0; i < e; i++)
	{
		int2 in;
		cin >> in.x >> in.y;
		Eva.push_back(in);
	}

	for (int i = 0; i < e; i++)
	{
		for (int k = Eva[i].x; k < Eva[i].y; k++)
		{
			common[k]++;
		}
	}

	int c = 0;
	vector<int2> ans;

	for (int i = 0; i < h; i++)
	{
		if (common[i] == 2)
		{
			c++;
			int k = i + 1;
			while (common[k] == 2)
			{
				k++;
			}
			int2 a;
			a.x = i + 1;
			a.y = k;
			ans.push_back(a);
			i = k;
		}
	}
	cout << c << endl;
	for (int2 a : ans)
	{
		cout << a.x << " " << a.y << endl;
	}
	cout << endl;
}